Recently, with increasing demand for electronic apparatuses in vehicles, applications of an HEV or an EV to large-sized vehicles and the like, needs for a high output in a rotating electrical machine such as a generator and a motor are high and a heating value of a stator winding or a rotor increases, so that measures against shortening of a life due to a temperature rise and the like become problems.
A method (liquid cooling type) of providing a cooling flow passage in a housing covering a stator is known as a method of cooling the rotating electrical machine and can effectively cool the stator in particular.
For the housing provided with the cooling flow passage, there are many casting products manufactured by a manufacturing method such as low pressure casting. In the manufacturing method, a premolded core (casting mold) is set to a mold, the core is pulverized and extracted after casting, and a cavity, that is, the flow passage is formed in the housing. This method has a problem in that productivity is low and a manufacturing cost is high.
With respect to the problems, PTL 1 discloses a two division structure in which a housing having an annular flow passage where a side of one direction of an axial direction is opened is provided, an opening end is closed by a bracket, and a cooling flow passage where cooling liquid circulates is formed, for the purpose of realizing a low cost and a simple structure. Because manufacturing is enabled using die-casting as a manufacturing method, a housing having a low cost and high productivity can be manufactured, as compared with the case of using the low pressure casting.
In addition, PTL 2 discloses a structure in which a hole penetrated in an axial direction is provided in a casing, the casing is interposed by brackets from both ends, and a flow passage of cooling water is formed inside.